阅读说明：本技术 改性核壳型氧化铝、聚氨酯复合材料及制备方法和应用 (Modified core-shell type aluminum oxide and polyurethane composite material, and preparation method and application thereof ) 是由 厉向杰 赵叶宝 帅丰平 陈俊 金美金 林孝杰 于 2019-09-24 设计创作，主要内容包括：本发明公开了一种改性核壳型氧化铝、聚氨酯复合材料及制备方法和应用,改性核壳型氧化铝,由氧化铝颗粒和包裹在其外的聚氨酯构成,聚氨酯复合材料是以包括多元醇混合物、改性核壳型氧化铝和异氰酸酯为原料制备的,其耐热性在180℃环境下热处理6h,抗拉强度和撕裂强度保持率达到70％以上,可应用于汽车发动机盖板。本发明在聚氨酯微孔弹性体中引入了表面改性的核壳型球型氧化铝,很好地解决了颗粒填料与聚氨酯原液相容性、分散性的问题,也柔化了球型氧化铝坚硬的表面,大幅增加了材料基体的热分解温度,从而保护聚氨酯本体,延长产品在高温环境下的使用寿命。(The invention discloses a modified core-shell type alumina, a polyurethane composite material, a preparation method and application thereof, wherein the modified core-shell type alumina is composed of alumina particles and polyurethane wrapped outside the alumina particles, the polyurethane composite material is prepared by taking a polyol mixture, the modified core-shell type alumina and isocyanate as raw materials, the heat resistance is subjected to heat treatment for 6 hours at 180 ℃, the retention rate of tensile strength and tear strength reaches more than 70%, and the modified core-shell type alumina can be applied to an automobile engine cover plate. According to the invention, the surface modified core-shell spherical alumina is introduced into the polyurethane microporous elastomer, so that the problems of compatibility and dispersibility of the particle filler and the polyurethane stock solution are well solved, the hard surface of the spherical alumina is softened, and the thermal decomposition temperature of the material matrix is greatly increased, thereby protecting the polyurethane body and prolonging the service life of the product in a high-temperature environment.)

1. The modified core-shell alumina is characterized by consisting of alumina particles and polyurethane wrapped outside the alumina particles.

2. The modified core-shell alumina of claim 1 wherein the alumina particles are spherical.

3. The modified core-shell alumina of claim 2 wherein the spherical alumina has a particle size of 5 to 50 μm.

4. The method for modifying core-shell alumina according to claim 1, comprising the steps of:

(1) treating said alumina particles with a coupling agent containing at least one amino or hydroxyl group;

(2) soaking the treated alumina particles in excessive isocyanate, reacting amino or hydroxyl on the surface of the treated alumina with the isocyanate, filtering, and drying in vacuum to obtain a modified material with the surface containing NCO groups;

(3) and (3) placing the modified material with the surface containing the NCO group obtained in the step (2) into an excessive compound which has a reactive group to isocyanate for reaction to obtain the modified core-shell type alumina.

5. The method according to claim 4, wherein the reaction temperature in the step (2) is 70-75 ℃ and the reaction time is 2-3 h; in the step (3), the reaction temperature is 70-75 ℃, and the reaction time is 2-3 h.

6. The method of claim 4, wherein in step (1), the method of treating the alumina particles with the coupling agent comprises the steps of: dispersing the alumina particles into an ethanol water solution with the mass ratio of 5: 1-2: 1, and adding acetic acid to adjust the pH value to 3-5; adding ethanol solution containing 1.0-2.0 wt% of the coupling agent; and (3) after reacting for 22-24 hours at the temperature of 20-25 ℃, and then collecting solids in the system.

7. The method of claim 6, wherein the ratio of the mass of the alumina particles to the volume of the aqueous ethanol solution is 1:20 to 100;

the volume ratio of the ethanol aqueous solution to the ethanol solution containing 1.0-2.0 wt% of the coupling agent is 1: 1-10: 1; the coupling agent is a silane coupling agent containing at least one amino group or hydroxyl group, and in the step (2), the isocyanate is isocyanate with 4 to 20 carbon atoms.

8. The method according to claim 7, wherein the silane coupling agent is one or more of γ -aminopropyltriethoxysilane, γ -aminopropyltrimethoxysilane, N- (β -aminoethyl) - γ -aminopropyltriethoxysilane, anilinomethyltriethoxysilane, anilinopropyltriethoxysilane, γ -aminopropylmethyldiethoxysilane, N- (β -aminoethyl) - γ -aminopropylmethyldimethoxysilane, N-ethyl-3-trimethoxysilane-2-methylpropylamine, anilinopropyltrimethoxysilane, anilinopropylmethyldimethoxysilane, γ -ureidopropyltriethoxysilane, and γ -ureidopropyltrimethoxysilane;

the isocyanate is more than one of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide modified diphenylmethane diisocyanate, uretonimine modified diphenylmethane diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate and methylene bis (cyclohexyl diisocyanate);

in the step (3), the compound of the group reactive to isocyanate is water and/or polyol (I) containing an average functionality of 1-4, the average hydroxyl value of the compound of the group reactive to isocyanate is 14-6233 mgKOH/g, and the polyol (I) is one or more of small molecular alcohol, polyester polyol and polyether polyol.

9. The method according to claim 8, wherein the small molecule alcohol is one or more of C1-C18 monohydric alcohol, C1-C18 monohydric alcohol amine, C1-C18 dihydric alcohol, C1-C18 dihydric alcohol amine, C1-C18 trihydric alcohol, C1-C18 trihydric alcohol amine;

the polyester polyol is prepared by esterification and polycondensation reaction of organic dicarboxylic acid containing 2-14 carbon atoms and polyhydric alcohol containing 2-14 carbon atoms;

the organic dicarboxylic acid is more than one of adipic acid, succinic acid, glutaric acid, suberic acid, sebacic acid, azelaic acid, phthalic acid, terephthalic acid, isophthalic acid, lauric acid, maleic acid and fumaric acid;

the polyhydric alcohol containing 2-14 carbon atoms is more than one of ethylene glycol, diethylene glycol, 1, 2-or 1, 3-propylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, glycerol and trimethylolpropane;

the polyester polyol can also be more than one of polycaprolactone polyol or polycarbonate polyol;

the polyether polyol is more than one of polypropylene oxide polyol, polyethylene oxide-propylene oxide copolymer polyol, polytetrahydrofuran diol, polytetrahydrofuran copolymer diol, polytrimethylene ether glycol and polymer polyol.

10. A polyurethane composite material prepared from a mixture comprising a polyol, the modified core-shell alumina according to claim 1 or 2, and an isocyanate.

11. The polyurethane composite material as claimed in claim 10, wherein the molar ratio of the mole number of active hydrogen to the mole number of isocyanate group (NCO) in isocyanate in the polyol mixture and the modified core-shell type alumina is 1 (1-1.05); the mass ratio of the polyol mixture to the modified core-shell alumina is 100 (1-100);

the polyol mixture comprises, in parts by weight:

the oligomer polyol A is polyester polyol (II) and/or polyether polyol (II) with the average functionality of 2-3 and the average hydroxyl value of 28.05-112.2 mgKOH/g;

the polyester polyol (II) is prepared by esterification and polycondensation reaction of more than one of ethylene glycol, diethylene glycol, 1, 2-or 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, hydroxyethylated bisphenol A, glycerol and trimethylolpropane and more than one of adipic acid, sebacic acid, succinic acid, suberic acid, glutaric acid, azelaic acid, phthalic acid, terephthalic acid and isophthalic acid; the polyether polyol (II) is more than one of polypropylene oxide polyol, polyethylene oxide-propylene oxide copolymer polyol, polytetrahydrofuran diol, polytetrahydrofuran copolymer diol, polytrimethylene ether glycol and polymer polyol;

the chain extender is more than one of ethylene glycol, diethylene glycol, 1, 2-or 1, 3-propylene glycol, 1, 4-butanediol, 1, 6-hexanediol, hydroquinone dihydroxyethyl ether (HQEE), Trimethylolpropane (TMP), glycerol, ethanolamine, diethanolamine, triethanolamine and triisopropanolamine;

the foaming agent is more than one of water, cyclopentane and 141B;

the foam stabilizer is a silicone oil foam stabilizer;

the isocyanate is diisocyanate or isocyanate prepolymer blocked by NCO;

the NCO-terminated isocyanate prepolymer is a reaction product of diisocyanate and oligomer polyol B, and the NCO content is 15-35%;

the weight ratio of the diisocyanate to the oligomer polyol B is (40-99) to (1-60).

12. The polyurethane composite according to claim 11, wherein the diisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, uretonimine-modified diphenylmethane diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, and methylene bis (cyclohexyl diisocyanate);

the oligomer polyol B is polyester polyol (II) and/or polyether polyol (II) with the average functionality of 2-3 and the average hydroxyl value of 28.05-112.2 mgKOH/g.

13. The polyurethane composite of claim 11, wherein the reaction of the diisocyanate and the oligomeric polyol B is further added with a side reaction inhibitor, wherein the side reaction inhibitor is phosphoric acid; the amount of the side reaction inhibitor added is 1ppm to 100ppm based on the total mass of the isocyanate and the oligomer polyol B.

14. The polyurethane composite material according to claim 11, wherein the modified core-shell alumina/polyurethane composite material further comprises a catalyst, and the amount of the catalyst added is 0.1-2.0 wt% of the total mass of the modified core-shell alumina and the polyol mixture; the catalyst is more than one of organic tin catalyst, organic bismuth catalyst and alcohol solution of triethylene diamine.

15. The method of preparing a polyurethane composite according to claim 14, comprising the steps of:

(1) mixing oligomer polyol A, a chain extender, a foaming agent and a foam stabilizer, and discharging to obtain a polyol mixture;

(2) uniformly mixing the polyol mixture, the modified core-shell alumina and the catalyst, wherein the mixing temperature depends on the operating environment temperature and the crystallization condition of the polyol mixture, and the polyol mixture is kept in a liquid state;

(3) controlling the temperature of the product obtained in the step (2) to be (15-55) DEG C, controlling the temperature of isocyanate to be (15-55) DEG C, setting the mixing ratio according to the molar ratio of the active hydrogen in the polyol mixture and the modified core-shell type alumina to the isocyanate group (NCO) in the isocyanate to be 1 (1-1.05), mixing, metering and injecting the mixture into a mold of (40-70) DEG C according to the molding density and the specification of the mold, reacting for (3-8) min for molding, demolding, and curing for (45-50) h to obtain the modified core-shell type alumina/polyurethane composite material.

16. Use of the polyurethane composite according to any one of claims 11 to 14 for the production of automotive engine covers with a molding density of 0.15 to 0.50g/cm³(ii) a Testing according to GB/T6343; the heat resistance is heat treatment for 6 hours under the environment of 180 ℃, and the retention rate of tensile strength and tearing strength reaches more than 70%.

Technical Field

The invention relates to a polyurethane composite material, a preparation method and application thereof.

Background

The polyurethane elastomer has excellent performances of high strength, good toughness, wear resistance, oil resistance and the like, and is widely applied to various fields of industrial production. The polyurethane elastomer has poor heat resistance, the service temperature is about 80 ℃, and the polyurethane elastomer can be used only for a short time at 120 ℃. The heat resistance of the polyurethane elastomer mainly depends on the thermal stability of each group in a molecular chain, wherein the thermal decomposition temperatures of biuret and allophanate are 144 ℃ and 146 ℃ respectively, so that the polyurethane elastomer is easy to thermally decompose in a high-temperature environment, and the original physical and mechanical properties, elasticity and the like are lost. Currently, the commonly used methods for improving heat resistance are: (1) introducing organic heterocyclic groups with larger cohesive energy and higher degradation temperature, such as isocyanate rings, oxazolidone rings, polyimide rings, organic silicon and fluorocarbon groups and the like, into a polyurethane molecular chain; (2) introducing a group containing high thermal degradation temperature into a polymer polyol; (3) epoxy resin, phenolic resin or acrylic resin and the like are blended with polyurethane or form an interpenetrating polymer network structure; (4) introduction of nano SiO₂Nano CaCO, nano-grade CaCO₃And fillers such as attapulgite and quartz. For example, the chinese patent application No. 201711271454.2 discloses that nano aluminum hydroxide is treated with a coupling agent, then coated with a modifier, and then mixed with polyurethane uniformly and then subjected to a composite treatment in an electric field to obtain a mixture; and then uniformly mixing the nano aluminum hydroxide with chloroprene rubber, a cross-linking agent, zinc stearate and tetrabutyl titanate, and performing composite treatment to obtain a composite modified polyurethane material, namely improving the compatibility of the nano aluminum hydroxide and polyurethane through a modifier, a coupling agent and a cross-linking agent, so that the polyurethane has better high-temperature resistance enhancing effect. A process for preparing heat-conducting plastics from spherical alumina filled polyurethane includes such steps as adding spherical alumina or spherical alumina modified by silane coupling agent KH-560 to polyol mixture (component A) and isocyanate (component B) to obtain composite material, and filling alumina in said composite materialThe effect of charge, surface treatment on the thermal conductivity properties of the composite. Research results show that when the filling amount is low, the thermal conductivity coefficient of the composite material filled with the alumina with large particle size is higher than that of the composite material with small particle size; at high loading levels, the small particle size alumina loading is higher than the large particle size loading. The treatment of alumina particles with the coupling agent KH-560 has some, but not significant, effect on the thermal conductivity of the polyurethane composite. Therefore, spherical alumina is a known technology as a heat-conducting filler, which can improve the heat resistance of polyurethane materials, but spherical alumina has high hardness, greatly wears molds during use, seriously damages the service life of the molds, and causes great cost burden for enterprises.

Disclosure of Invention

The invention aims to provide a modified core-shell type aluminum oxide and polyurethane composite material, a preparation method and application thereof, so as to overcome the defects in the prior art.

The modified core-shell alumina consists of alumina particles and polyurethane wrapped outside the alumina particles;

preferably, the alumina particles are spherical;

the modification method of the modified core-shell alumina comprises the following steps:

(1) treating said alumina particles with a coupling agent containing at least one amino or hydroxyl group;

(2) soaking the treated alumina particles in excessive isocyanate, reacting amino or hydroxyl on the surfaces of the treated alumina particles with the isocyanate, filtering, and drying in vacuum to obtain a modified material with NCO groups on the surfaces;

(3) placing the modified material with the surface containing NCO groups obtained in the step (2) into an excessive compound which has reactive groups to isocyanate for reaction to obtain the modified core-shell type alumina;

preferably, the alumina is spherical, and the particle size of the spherical alumina is 5-50 μm;

in the step (2), the reaction temperature is 70-75 ℃, and the reaction time is 2-3 h;

in the step (3), the reaction temperature is 70-75 ℃, and the reaction time is 2-3 h.

In step (1), the method for treating alumina particles by using the coupling agent comprises the following steps:

dispersing the aluminum oxide into an ethanol water solution with the mass ratio of 5: 1-2: 1, and adding acetic acid to adjust the pH value to 3-5; adding ethanol solution containing 1.0-2.0 wt% of the coupling agent; reacting for 22-24 hours at 20-25 ℃, and then collecting solids in the system; preferably, the ethanol solution containing 1.0-2.0 wt% of the coupling agent is added dropwise

The mass ratio of the alumina particles to the volume of the ethanol aqueous solution is 1: 20-100;

the volume ratio of the ethanol aqueous solution to the ethanol solution containing 1.0-2.0 wt% of the coupling agent is 1: 1-10: 1;

the coupling agent is a silane coupling agent containing at least one amino or hydroxyl;

preferably, the silane coupling agent is more than one of gamma-aminopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane, N- (beta-aminoethyl) -gamma-aminopropyltriethoxysilane, aniline methyl triethoxysilane, aniline propyl triethoxysilane, gamma-aminopropylmethyldiethoxysilane, N- (beta-aminoethyl) -gamma-aminopropylmethyldimethoxysilane, N-ethyl-3-trimethoxysilane-2-methylpropylamine, aniline propyl trimethoxysilane, aniline propyl methyldimethoxysilane, gamma-urea propyl triethoxysilane and gamma-urea propyl trimethoxysilane;

in the step (2), the isocyanate is isocyanate having 4 to 20 carbon atoms;

preferably, the isocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, uretonimine-modified diphenylmethane diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, and methylene bis (cyclohexyl diisocyanate);

in the step (2), the term "treated spherical alumina is soaked in excess isocyanate", wherein excess means that complete reaction of amino or hydroxyl on the treated spherical alumina is ensured;

in the step (3), the term "placing the modified material with the surface containing NCO groups obtained in the step (2) into excessive compounds with reactive groups to isocyanate", wherein excessive means ensuring that the NCO groups on the surface of the modified material are completely reacted;

in the step (3), the compound of the group reactive to isocyanate is water and/or polyol (I) containing 1-4 average functionality, and the average hydroxyl value of the compound of the group reactive to isocyanate is 14-6233 mgKOH/g. The polyol (I) is more than one of micromolecular alcohol, polyester polyol and polyether polyol;

the small molecular alcohol can be more than one of C1-C18 monohydric alcohol, C1-C18 monohydric alcohol amine, C1-C18 dihydric alcohol, C1-C18 dihydric alcohol amine, C1-C18 trihydric alcohol and C1-C18 trihydric alcohol amine;

the polyester polyol is prepared by esterification and polycondensation reaction of organic dicarboxylic acid containing 2-14 carbon atoms and polyhydric alcohol containing 2-14 carbon atoms;

the organic dicarboxylic acid is more than one of adipic acid, succinic acid, glutaric acid, suberic acid, sebacic acid, azelaic acid, phthalic acid, terephthalic acid, isophthalic acid, lauric acid, maleic acid and fumaric acid;

the polyhydric alcohol containing 2-14 carbon atoms is more than one of ethylene glycol, diethylene glycol, 1, 2-or 1, 3-propylene glycol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, glycerol and trimethylolpropane;

the polyester polyol can also be more than one of polycaprolactone polyol or polycarbonate polyol;

the polyether polyol is more than one of polypropylene oxide polyol, polyethylene oxide-propylene oxide copolymer polyol, polytetrahydrofuran diol, polytetrahydrofuran copolymer diol, polytrimethylene ether glycol and polymer polyol;

the invention also relates to a polyurethane composite material which is prepared by taking a polyol mixture, the modified core-shell alumina and isocyanate as raw materials;

in the polyol mixture and the modified core-shell alumina, the molar ratio of the mole number of active hydrogen to the mole number of isocyanate groups (NCO) in isocyanate is 1 (1-1.05); the mass ratio of the polyol mixture to the modified core-shell alumina is (1-100). Preferably, the mass ratio of the polyol mixture to the modified core-shell alumina is 10 (1-5).

The polyol mixture contains, in parts by weight

The oligomer polyol A is polyester polyol (II) and/or polyether polyol (II) with the average functionality of 2-3 and the average hydroxyl value of 28.05-112.2 mgKOH/g;

the polyester polyol (II) is prepared by esterification and polycondensation reaction of more than one of ethylene glycol, diethylene glycol, 1, 2-or 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, hydroxyethylated bisphenol A, glycerol and trimethylolpropane and more than one of adipic acid, sebacic acid, succinic acid, suberic acid, glutaric acid, azelaic acid, phthalic acid, terephthalic acid and isophthalic acid; the polyether polyol (II) is more than one of polypropylene oxide polyol, polyethylene oxide-propylene oxide copolymer polyol, polytetrahydrofuran diol, polytetrahydrofuran copolymer diol, polytrimethylene ether glycol and polymer polyol.

The chain extender is more than one of ethylene glycol, diethylene glycol, 1, 2-or 1, 3-propylene glycol, 1, 4-butanediol, 1, 6-hexanediol, hydroquinone dihydroxyethyl ether (HQEE), Trimethylolpropane (TMP), glycerol, ethanolamine, diethanolamine, triethanolamine and triisopropanolamine;

the foaming agent is more than one of water, cyclopentane and 141B;

the foam stabilizer is a silicone oil foam stabilizer.

The isocyanate is diisocyanate or isocyanate prepolymer blocked by NCO;

the NCO-terminated isocyanate prepolymer is a reaction product of diisocyanate and oligomer polyol B, and the NCO content is 15-35%;

the weight ratio of the diisocyanate to the oligomer polyol B is (40-99) to (1-60);

the reaction temperature of the diisocyanate and the oligomer polyol B is (60-80) DEG C, and the reaction time is (2-3) h;

the reaction of the diisocyanate and the oligomer polyol B can be carried out, and a side reaction inhibitor can be added, wherein the side reaction inhibitor is phosphoric acid; the amount of the side reaction inhibitor added is 1ppm to 100ppm based on the total mass of the isocyanate and the oligomer polyol B.

The diisocyanate is more than one of toluene diisocyanate, diphenylmethane diisocyanate, carbodiimide modified diphenylmethane diisocyanate, uretonimine modified diphenylmethane diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate and methylene bis (cyclohexyl diisocyanate).

The oligomer polyol B is polyester polyol (II) and/or polyether polyol (II) with the average functionality of 2-3 and the average hydroxyl value of 28.05-112.2 mgKOH/g;

preferably, the modified core-shell alumina/polyurethane composite material further comprises a catalyst, and the addition amount of the catalyst is 0.1 wt% -2.0 wt% of the total mass of the modified core-shell alumina and the polyol mixture; the catalyst is more than one of organic tin catalyst, organic bismuth catalyst and alcoholic solution of triethylene diamine;

the preparation method of the polyurethane composite material comprises the following steps:

(1) mixing oligomer polyol A, a chain extender, a foaming agent and a foam stabilizer at the temperature of 40-45 ℃ for 2.5-3.5 h, discharging, sealing and storing to obtain a polyol mixture;

(2) uniformly mixing the polyol mixture, the modified core-shell alumina and the catalyst, wherein the mixing temperature depends on the operating environment temperature and the crystallization condition of the polyol mixture, and the polyol mixture is kept in a liquid state;

(3) controlling the temperature of the product obtained in the step (2) to be (15-55) DEG C, controlling the temperature of isocyanate to be (15-55) DEG C, setting the mixing ratio according to the mole number of active hydrogen in a polyol mixture and modified core-shell type alumina and the mole ratio of isocyanate group (NCO) in the isocyanate to be 1 (1-1.05), quickly and fully mixing, metering and injecting the mixture into a mold at the temperature of (40-70) DEG C according to the molding density and the specification of the mold, reacting for (3-8) min for molding, demolding, curing for (45-50) h, and obtaining the modified core-shell type alumina/polyurethane composite material.

The molding density of the polyurethane composite material is 0.15-0.50g/cm³(ii) a Testing according to GB/T6343;

the heat resistance of the core-shell type aluminum oxide/polyurethane composite material is 6 hours of heat treatment at 180 ℃, the retention rate of tensile strength and tear strength reaches more than 70%, and the core-shell type aluminum oxide/polyurethane composite material can be applied to the preparation of automobile engine cover plates.

The invention has the beneficial effects that:

the invention introduces the surface modified core-shell spherical alumina into the polyurethane microporous elastomer. Firstly, the problems of compatibility and dispersibility of the particle filler and a polyurethane stock solution are well solved by a modification mode of the surface of the core-shell spherical alumina; meanwhile, the existence of the polyurethane structural shell also softens the hard surface of the spherical alumina, avoids mechanical damage to equipment, molds and the like, and improves operability. Secondly, the thermal decomposition temperature of the material matrix is greatly increased due to the introduction of the core-shell spherical alumina, and meanwhile, the spherical alumina plays a role in supporting a rigid chain segment, so that the softening temperature of the matrix is further increased.

Drawings

FIG. 1 shows a molding density of 0.15g/cm³Free cup foaming effect under the formula, (a) is the foaming effect when the using amount of the polyol mixture is large; (b) the free cup does not collapse and shrink as a foaming center, and the ratio of active hydrogen in the polyol mixture to NCO groups in isocyanate is the most appropriate; (c) the foaming effect is obtained when the amount of isocyanate used is large.

FIG. 2 shows a molding density of 0.50g/cm³Free cup foaming effect under the formula, (a) is the foaming effect when the using amount of the polyol mixture is large; (b) the free cup does not collapse and shrink as a foaming center, and the ratio of active hydrogen in the polyol mixture to NCO groups in isocyanate is the most appropriate; (c) the foaming effect is obtained when the amount of isocyanate used is large.

FIG. 3 shows a molded density of 0.30g/cm³The majority of oligomer polyols are free cup foaming effects under the formulation of polyester polyols, and (a) is the foaming effect when the polyol mixture is used in a large amount; (b) the free cup does not collapse and shrink as a foaming center, and the ratio of active hydrogen in the polyol mixture to NCO groups in isocyanate is the most appropriate; (c) the foaming effect is obtained when the amount of isocyanate used is large.

FIG. 4 shows a molding density of 0.30g/cm³The majority of the oligomer polyol is the free cup foaming effect under the formula of polyether polyol, and (a) is the foaming effect when the using amount of the polyol mixture is large; (b) the free cup does not collapse and shrink as a foaming center, and the ratio of active hydrogen in the polyol mixture to NCO groups in isocyanate is the most appropriate; (c) the foaming effect is obtained when the amount of isocyanate used is large.

Detailed Description

The present invention is further illustrated by the following specific examples, but it should be understood that the specific materials, process conditions and results described in the examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and all equivalent changes and modifications made according to the spirit of the present invention should be covered by the scope of the present invention.

Preparing modified core-shell spherical alumina: